A few years ago I was on the Power Kid Podcast and shared time with the original inventor of the Nerf ball and foam, Reyn Guyer!
He gives the origin of the Nerf name, and *spoiler* NERF DOES NOT mean “Non-Expanding Recreational Foam”. The story is a lot more…. Advertising.
Listen to the episode I linked, Reyn’s explanation of the Nerf origin begins at 21:26.